1. Field of the Invention
The present invention relates to a system and method for detecting driver drowsiness and generating an alarm when the driver becomes drowsy while the vehicle is moving at greater than a predetermined speed, and more particularly, a system and method comprising means for detecting and signalling the roughness of the road surface on which the vehicle is running and means for determining from an output signal of said detecting means that the vehicle is running on a rough road and interrupting the detection of drowsy driving, so as to prevent erroneous detection of drowsy driving due to the abnormal steering operations while running on the rough road.
2. Description of the Prior Art
Japanese Utility Model Registration Publication No. 57-57126 discloses a system for recognizing the vehicle driver drowsiness, wherein the system determines that the vehicle driver is driving drowsily depending on the number of steering pulses, each steering pulse being produced whenever the steering wheel is rotated through a predetermined angle, produced within a predetermined period of time. The disclosure of the above-described publication is incorporated herein by reference.
However, the system disclosed in the above-described publication may occasionally erroneously detect drowsiness. For example, when the vehicle is running on an unpaved road, the angular extent steering adjustments tends to be greater than when the vehicle is running on a paved road due to the necessity for the driver to correct the direction of the vehicle course a number of times due to the holes and bumps of the unpaved road surface. In such cases, steering adjustments tend to involve a large angle of steering in spite of driver alertness.
In more detail, while driving on rough roads, the system determines erroneously that the vehicle driver is drowsy because the number of steering pulses exceeds a predetermined number over a fixed interval of time.